Combine sugar and corn starch in a large bowl. Add rhubarb and apples and gently toss to coat. Spoon into a greased 8-inch square baking dish.
½ cup sugar, 3 tablespoons corn starch, 4 cups sliced fresh rhubarb, 2 cups apples
In a small bowl, combine oats, brown sugar, butter, cinnamon and flour until the mixture resembles coarse crumbs. Sprinkle over rhubarb mixture. Bake for 50 minutes or until bubbly and fruit is tender.
1 cup old-fashioned oats, ½ cup packed brown sugar, ½ cup butter, ½ cup all-purpose flour, 1 teaspoon ground cinnamon
Serve warm or at room temperature.
Notes
Use your favorite apple for this recipe. Granny Smith or Honeycrisp apples are always a solid choice.
Use gluten-free oats and flour to make this crisp GF.
Baking time can vary based on the temperature in your oven. Bake until the top is a brown as you want it and the fruit is tender.
Adjust the granulated sugar according to your apples and your preferences. If you want it more on the tart side, add a little less sugar. If you prefer sweeter desserts, add an additional ¼ cup sugar.
If you use frozen rhubarb, make sure you thaw it first and drain off the extra liquid so your crisp isn't runny.
Like a lot of streusel topping? Double the topping recipe for an extra thick layer.
If you are serving the crisp directly from the oven, let it sit for 15-20 minutes before serving to let the juices thicken.